In one embodiment, a method includes providing for presentation to a user a number of content objects. Some of the content objects are socially relevant to the user and some of the content objects are socially irrelevant to the user. The method also includes receiving input indicating a selection of one of the content objects by the user; determining whether the content object selected by the user is socially relevant to the user; authenticating the user if the content object selected by the user is socially relevant to the user; and declining to authenticate the user if the content object selected by the user is socially irrelevant to the user.